A large number of various components of printed circuit boards (PCBs) are mounted on a flat plate formed of a phenol or epoxy resin. Circuitries connecting the components to each other are closely fixed to a surface of the flat plate to form a circuit board.
In such a PCB, after a thin film formed of copper or the like is attached to a surface of a resin insulation plate, the resin insulation plate including the thin film is etched according to a wiring pattern of a circuit to obtain a desired circuit. Afterward, holes are bored for mounting components.
The PCB is classified into a single-sided board, a double-sided board, and a multilayered board depending on the number of wiring circuit board surfaces. As the number of layers is increased, the ability to mount components increases and more highly precise products can be realized.
An electro-optical circuit board (ECOB), in which optical waveguides that can transmit and receive optical signals using a polymer and a glass fiber are inserted into the PCB has been developed now.
According to a related art ECOB, an optical via hole is bored in an optical PCB in which optical waveguides are buried to insert an optical connection rod in which a reflection mirror is inclined at an angle of about 45° or an optical connection block in which a glass fiber is bent at an angle of about 90° into the optical via hole.
However, in the related art ECOB, it is difficult to precisely align the optical waveguides with the optical connection rod/optical connection block in vertical and horizontal directions and in left and right directions.
In addition, there are limitations that a plurality of layers should be stacked, and a drilling process should be required so as to insert the optical waveguide into the circuit board.